<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .embed-responsive {
      position: relative;
    }
    .embed-responsive iframe,
    .embed-responsive video {
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      border: 0;
    }
    .embed-responsive-16by9 {
      padding-bottom: 56.25%;
    }
    .embed-responsive-4by3 {
      padding-bottom: 75%;
    }
  </style>
</head>
<body>
  <div style="width: 500px;">
    <div class="embed-responsive embed-responsive-16by9">
      <iframe src="http://www.baidu.com"></iframe>
    </div>
  </div>
</body>
</html>